Method for forming a hemispherically shaped switch assembly

Abstract

A hemispherically shaped membrane switch assembly for attaching to generally hemispherical surfaces such as cathode ray tubes is disclosed. Also disclosed are a method and apparatus for forming the assembly. The assembly is comprised of two layers of transparent film having spaced-apart conductors on the internal surfaces of both layers. The internal surfaces are separated by spacing means, the spacing means being discontinuous at the switch sites. The conductors on the two layers cross and are spaced apart at the switch sites. The assembly is hemispherically formed to the same radius as the hemispherical surface on which the assembly is to be mounted. The assembly mounts flush to the hemispherical surface and conforms uniformly to its surface thus reducing distortion and parallax.

What is claimed is: 
     
       1. A method for forming flexible film for attaching to generally hemispherical surfaces, the film being of the type used in membrane switches, one side of the film having electrical conductors thereon, the method being characterized by the steps of: applying conductors to one surface of a flat flexible film, to form a circuit layer,   placing the flexible film circuit layer between two parallel retaining layers of thermoplastic film, the periphery of the circuit layer being freely held between the two retaining layers,   clamping the retaining layers of film between concave and convex surfaces,   transferring heat to at least one surface of the retaining layers until the circuit layer attains a hemispherical shape,   applying a vacuum to the concave surface to hold the circuit layer in its formed condition as the heat is removed and the flexible film circuit layer is allowed to cool.   
     
     
       2. The method for forming flexible film for attaching to generally hemispherical surfaces as recited in claim 1, wherein the conductors are narrow electrodeposited conductors. 
     
     
       3. The method for forming flexible film for attaching to generally hemispherical surfaces as recited in claim 1 wherein the conductors are narrow screened ink conductors. 
     
     
       4. The method for forming flexible film for attaching to generally hemispherical surfaces as recited in claim 1, wherein a sheet of freely held flexible mesh is placed between the circuit layer and the lower retaining layer.